Table 2. Quality assessment based on the Newcastle-Ottawa Scale of studies included in this meta-analysisa.
| Author | Year | Adequate definition of case | Representativeness of cases | Selection of control | Definition of control | Control for important factor or additional factorb | Exposure assessment | Same method of ascertainment for cases and controls | Nonresponse rate | Total quality scores |
|---|---|---|---|---|---|---|---|---|---|---|
| Abe A[17] | 2002 | ★ | ★ | ★ | ★ | ★ | 5 | |||
| Bruyère F[18] | 2010 | ★ | ★ | ★ | ★ | ★ | 5 | |||
| Sáenz-López P[19] | 2013 | ★ | ★ | ★ | ★ | ★ | ★ | 6 | ||
| Shen BL[20] | 2015 | ★ | ★ | ★ | ★ | ★ | 5 | |||
| Lu GJ[21] | 2015 | ★ | ★ | ★ | ★ | ★ | 5 | |||
| Xian W[22] | 2015 | ★ | ★ | ★ | ★ | ★ | 5 | |||
| Ajaz S[23] | 2011 | ★ | ★ | ★ | ★ | ★ | 5 | |||
| Ricketts C[24] | 2009 | ★ | ★ | ★ | ★ | ★ | ★ | 6 |
a
A study can be awarded a maximum of one star for each numbered item except for the item Control for important factor or additional factor.
b
A maximum of two stars can be awarded for Control for important factor or additional factor.